Models by Jean Biarez for the Behavior of Clean Sands and Remolded Clays at Large Strains - Multiscale Geomechanics: From Soil to Engineering Projects - page 141

5.9.2.2. Biarez's mixed model in Burland's space (I v - log σ ' v )

e C are replaced by
expressions [5.29] proposed by Burland for the ICL expression [FAV 08]. This
gives the “mixed” model [5.35]:

In the linear relation [5.31] resulting from Biarez,

100 and

* *

c

[ ]

= 0.46 3 log ' − σ − χ

. [5.35]

V

Here ζ and χ are the parameters given by [5.36] as a function of the e L and e P
limits, defined by their experimental values:

 ee

e

−

=

L P



0.256 0.04
0.109 0.679

−

 L

[5.36]

+ − 0.089

2

+ 0.016

3

−

χ = .

L L L P

0.256 − 0.04

L

P e = is not considered, the NCRS a line is not forced
to pass through a point on the ICL. The NCRS a line, however, will depend on the e L
limit.

Since the assumption of

*
1000

When equation [5.35] is applied to the kaolinite through the e L value ( w L = 40%
and w P = 20%), we obtain a curve termed NCRS a/k , located very close to the ICL
(see Figure 5.21a), whatever the stress domain may be. Both correlations are thus
very similar, and compatible with the experimental curve on the oedometric path
(see Figure 5.21a), the kaolinite having first been consolidated under one-
dimensional conditions under an axial stress of 140 kPa.

The NCRS a/m-s curve calculated for the GoG marine sediments (the deepwater
sediments from the Gulf of Guinea, whose w L and w P limits vary according to depth,
therefore according to σ ' v , from 110% to 160% for w L and from 30% to 90% for w P
[FAV 06]) diverges from the ICL, but also from the experimental curve
(Figure 5.21a). The experimental path evolves first from one point located above the
ICL curve (sensitive clays) and also the NCRS a/m-s . This point (which exhibits a
“fictitious consolidation stress” and a supplementary cohesion on the oedometric
curve) is associated with the beginning of the damage of the cementation
(destructuration according to Leroueil et al. [LER 79]), developed in situ during the
sedimentation and consolidation processes. The experimental curves thus tend to
converge at high stresses towards the ICL curve of the remolded state of the
material.

The principal difference between the ICL and the NCRS, on one hand, and
NCRS a/m-s on the other hand, seems to be due mainly to the difference between the